In a load driving arrangement that drives a load (for example, a motor, solenoid, etc.) based on a control signal from a controller, a fault diagnosis system using a driver that is provided with a self-diagnosis function to detect a fault in the load driving arrangement has recently been put into practical use.
Such fault diagnosis system is, for example, comprised of a load (e.g., a motor) 111, a driver 112 for driving the load 111, and a controller (e.g., an engine ECU) 113 which controls the driving of the load 111, as is shown in FIG. 20. This system is arranged such that a Hi (High) level control signal is sent from the controller 113 to the driver 112 when it is desired to drive the load 111 at a high speed, a Lo (Low) level control signal is sent from the controller 113 to the driver 112 when it is desired to drive the load 111 at a low speed, and the driver 112 drives the load 111 at a high or low speed, based on the corresponding signal.
Then, if there is not fault in the load 111 and the driver 112, the driver 112 returns a Hi level monitor signal to the controller 113, and if there is a fault, the driver 112 returns a Lo level monitor signal to the controller 113. The controller 113 is adapted to perform fault diagnosis of the load 111 and the driver 112 according to the monitor signal.
This fault diagnosis system is applied to, particularly, e.g., a fuel pump control system of a vehicle. In this application, the load 111 is a fuel pump (pump motor), the driver 112 is a fuel pump controller, and the controller 113 is an engine ECU.